CVE-2026-34486
CVE-2026-34486 is a security flaw in Apache Tomcat, a server for running Java web applications. Attackers can read information from Apache Tomcat that should be private. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 4 Aug 2026.[1]
Apache Tomcat is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Apache has published a fix or advice.
Description
CISA calls it a missing encryption of sensitive data in Apache Tomcat. In its words: “Apache Tomcat contains a missing encryption of sensitive data vulnerability that allows the bypass of the EncryptInterceptor. This vulnerability can be chained with CVE‑2025‑24813.”[1]
The CVE record adds: “Missing Encryption of Sensitive Data vulnerability in Apache Tomcat due to the fix for CVE-2026-29146 allowing the bypass of the EncryptInterceptor. This issue affects Apache Tomcat: 11.0.20, 10.1.53, 9.0.116. Users are recommended to upgrade to version 11.0.21, 10.1.54 or 9.0.117, which fix the issue.”[2]
The underlying weakness is CWE-311, in MITRE’s list of common software weaknesses.
It scores 7.5 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Apache’s advisory has them[3]. CISA names the product as Apache Tomcat.
Most families won’t have Apache Tomcat; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 4 Aug 2026, 117 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 7 Aug 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Apache has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]
- Check whether you use it.Apache Tomcat is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 7 Aug 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 99%.[4] |
See also
Other Apache Tomcat flaws
- CVE-2025-24813: path equivalence ·
- CVE-2016-8735: remote code execution ·
- CVE-2017-12617: remote code execution ·
- CVE-2017-12615: on windows remote code execution ·
- CVE-2020-1938: improper privilege management ·
Other Apache flaws
- CVE-2016-3081, Apache Struts: command injection ·
- CVE-2026-34197, Apache ActiveMQ: improper input validation ·
- CVE-2024-38475, Apache HTTP Server: improper escaping of output ·
- CVE-2024-45195, Apache OFBiz: forced browsing ·
- CVE-2024-27348, Apache HugeGraph-Server: improper access control ·
Added the same day
- CVE-2026-9198, IBM Langflow: code injection ·
- CVE-2026-18556, N-able N-central: authentication bypass using an alternate path or channel ·
Every Apache flaw on CISA’s list · Everything added in August 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apache Tomcat Missing Encryption of Sensitive Data Vulnerability”. Known Exploited Vulnerabilities Catalog, added 4 Aug 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-34486 Detail”. National Vulnerability Database, published 9 Apr 2026.
- ^ Apache. Advisories and fixes: lists.apache.org, vicarius.io.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.985, percentile 99.9, 31 Oct 2026.
- CVE Program. “CVE-2026-34486”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.