'Dead simple' hijacking hole in Apache Tomcat 'now actively exploited in the wild'
(2025/03/18)
- Reference: 1742258679
- News link: https://www.theregister.co.uk/2025/03/18/apache_tomcat_java_rce_flaw/
- Source link:
A trivial flaw in Apache Tomcat that allows remote code execution and access to sensitive files is said to be under attack in the wild within a week of its disclosure.
The vulnerability is [1]CVE-2025-24813 , and was revealed on March 10 along with updates to close the hole in the open source web server software. According to API security shop Wallarm, an exploit for the bug was publicly distributed 30 hours later, and is “now actively exploited in the wild.”
Authentication is not required to pull off an attack, and the end result is the ability to run arbitrary code on the targeted Tomcat server by miscreants, allowing them to access data among other nefarious things.
[2]
"We've already seen this in operation by Chinese operators, and CISA [The US government's Cybersecurity and Infrastructure Security Agency] got in touch tonight and are going to add the exploit to its warning list," Ivan Novikov, Wallarm's CEO, told The Register .
[3]
[4]
According to a Wallarm [5]advisory about the flaw, the only requirement for successful exploitation “is that Tomcat is using file-based session storage, which is common in many deployments.”
“The attacker starts by sending a PUT request to upload a malicious session file to the server,” Wallarm’s advisory explains.
[6]
"The payload is a base64-encoded ysoserial gadget chain, designed to trigger remote code execution when deserialized. This request writes a file inside Tomcat’s session storage directory. Because Tomcat automatically saves session data in files, the malicious payload is now stored on disk, waiting to be deserialized.”
To deserialize the payload, attackers need only send a GET request with the JSESSIONID pointing to the malicious session. “Tomcat, seeing this session ID, retrieves the stored file, deserializes it, and executes the embedded Java code, granting full remote access to the attacker,” Wallarm’s advisory states.
[7]200-plus impressively convincing GitHub repos are serving up malware
[8]Patch now: RCE Spring4shell hits Java Spring framework
[9]Who is exploiting VMware right now? Probably Iran's Rocket Kitten, to name one
[10]Rather than add a backdoor, Apple decides to kill iCloud encryption for UK peeps
The Apache Foundation’s [11]advisory on the matter rates this an “important” flaw. The foundation doesn’t assign CVSS scores – preferring to provide details that allow users to make their own decisions about how to act.
The org points out that successful exploitation of the flaw to achieve remote code execution requires four conditions to be met, including two default settings in Tomcat - writes enabled to the default servlet and support for partial PUT uploads. The other two conditions are an application configured to use Tomcat's file based session persistence with the default storage location and including a library that may be leveraged in a deserialization attack.
That's a decent set of hurdles though crims may find the course worthwhile as Apache Tomcat is widely used to deploy bespoke Java applications inside enterprises. Such apps store the kind of juicy data and code network intruders love to pillage. Running Tomcat in read-only mode for the default servlet has been [12]a good idea since at least 2017.
[13]
The flaw is present in Apache Tomcat versions 11.0.0-M1 through 11.0.2, from 10.1.0-M1 through 10.1.34, and from 9.0.0.M1 through 9.0.98.
The flaw can also be used to view or tamper with sensitive files. That scenario requires five conditions to be met:
Writes enabled for the default servlet (disabled by default)
Support for partial PUT (enabled by default)
A target URL for security sensitive uploads that was a sub-directory of a target URL for public uploads
Attacker knowledge of the names of security sensitive files being uploaded
The security sensitive files also being uploaded via partial PUT
We've asked Apache for more info and will update this story if the org responds. ®
Get our [14]Tech Resources
[1] https://nvd.nist.gov/vuln/detail/CVE-2025-24813
[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
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[5] https://lab.wallarm.com/one-put-request-to-own-tomcat-cve-2025-24813-rce-is-in-the-wild/
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[7] https://www.theregister.com/2025/02/26/infosec_bytes/
[8] https://www.theregister.com/2022/03/31/spring_vuln/
[9] https://www.theregister.com/2022/04/26/iran_rocket_kitten_vmware_exploit/
[10] https://www.theregister.com/2025/02/24/rather_than_add_a_backdoor/
[11] https://lists.apache.org/thread/j5fkjv2k477os90nczf2v9l61fb0kkgq
[12] https://secbot.com/docs/templates/tech/apache/tomcat/tomcat-readonly-rce
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[14] https://whitepapers.theregister.com/
The vulnerability is [1]CVE-2025-24813 , and was revealed on March 10 along with updates to close the hole in the open source web server software. According to API security shop Wallarm, an exploit for the bug was publicly distributed 30 hours later, and is “now actively exploited in the wild.”
Authentication is not required to pull off an attack, and the end result is the ability to run arbitrary code on the targeted Tomcat server by miscreants, allowing them to access data among other nefarious things.
[2]
"We've already seen this in operation by Chinese operators, and CISA [The US government's Cybersecurity and Infrastructure Security Agency] got in touch tonight and are going to add the exploit to its warning list," Ivan Novikov, Wallarm's CEO, told The Register .
[3]
[4]
According to a Wallarm [5]advisory about the flaw, the only requirement for successful exploitation “is that Tomcat is using file-based session storage, which is common in many deployments.”
“The attacker starts by sending a PUT request to upload a malicious session file to the server,” Wallarm’s advisory explains.
[6]
"The payload is a base64-encoded ysoserial gadget chain, designed to trigger remote code execution when deserialized. This request writes a file inside Tomcat’s session storage directory. Because Tomcat automatically saves session data in files, the malicious payload is now stored on disk, waiting to be deserialized.”
To deserialize the payload, attackers need only send a GET request with the JSESSIONID pointing to the malicious session. “Tomcat, seeing this session ID, retrieves the stored file, deserializes it, and executes the embedded Java code, granting full remote access to the attacker,” Wallarm’s advisory states.
[7]200-plus impressively convincing GitHub repos are serving up malware
[8]Patch now: RCE Spring4shell hits Java Spring framework
[9]Who is exploiting VMware right now? Probably Iran's Rocket Kitten, to name one
[10]Rather than add a backdoor, Apple decides to kill iCloud encryption for UK peeps
The Apache Foundation’s [11]advisory on the matter rates this an “important” flaw. The foundation doesn’t assign CVSS scores – preferring to provide details that allow users to make their own decisions about how to act.
The org points out that successful exploitation of the flaw to achieve remote code execution requires four conditions to be met, including two default settings in Tomcat - writes enabled to the default servlet and support for partial PUT uploads. The other two conditions are an application configured to use Tomcat's file based session persistence with the default storage location and including a library that may be leveraged in a deserialization attack.
That's a decent set of hurdles though crims may find the course worthwhile as Apache Tomcat is widely used to deploy bespoke Java applications inside enterprises. Such apps store the kind of juicy data and code network intruders love to pillage. Running Tomcat in read-only mode for the default servlet has been [12]a good idea since at least 2017.
[13]
The flaw is present in Apache Tomcat versions 11.0.0-M1 through 11.0.2, from 10.1.0-M1 through 10.1.34, and from 9.0.0.M1 through 9.0.98.
The flaw can also be used to view or tamper with sensitive files. That scenario requires five conditions to be met:
Writes enabled for the default servlet (disabled by default)
Support for partial PUT (enabled by default)
A target URL for security sensitive uploads that was a sub-directory of a target URL for public uploads
Attacker knowledge of the names of security sensitive files being uploaded
The security sensitive files also being uploaded via partial PUT
We've asked Apache for more info and will update this story if the org responds. ®
Get our [14]Tech Resources
[1] https://nvd.nist.gov/vuln/detail/CVE-2025-24813
[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
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[5] https://lab.wallarm.com/one-put-request-to-own-tomcat-cve-2025-24813-rce-is-in-the-wild/
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[7] https://www.theregister.com/2025/02/26/infosec_bytes/
[8] https://www.theregister.com/2022/03/31/spring_vuln/
[9] https://www.theregister.com/2022/04/26/iran_rocket_kitten_vmware_exploit/
[10] https://www.theregister.com/2025/02/24/rather_than_add_a_backdoor/
[11] https://lists.apache.org/thread/j5fkjv2k477os90nczf2v9l61fb0kkgq
[12] https://secbot.com/docs/templates/tech/apache/tomcat/tomcat-readonly-rce
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/cso&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33Z9j98e8-7pcEO11KTVVpgAAAAIU&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[14] https://whitepapers.theregister.com/