CVE-2024-23829: aiohttp's HTTP parser (the python one, not llhttp) still overly lenient about separators
Affects aiohttpSource GCVE Database
Not known to be exploited · CVSS 6.5 Medium : upgrade to 3.9.2 when convenient.
Data as of 29 Oct 2026, 22:52 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 6.5 |
|---|
- Patch
- Available – fixed in 3.9.2
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:LExploitation evidence
Disclosed: evidence found.
CVE published 3 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade aiohttp to 3.9.2.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| PyPIaiohttp | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
### Summary Security-sensitive parts of the *Python HTTP parser* retained minor differences in allowable character sets, that must trigger error handling to robustly match frame boundaries of proxies in order to protect against injection of additional requests. Additionally, validation could trigger exceptions that were not handled consistently with processing of other malformed input. ### Details These problems are rooted in pattern matching protocol elements, previously improved by PR #3235 and GHSA-gfw2-4jvh-wgfg: 1. The expression `HTTP/(\d).(\d)` lacked another backslash to clarify that the separator should be a literal dot, not just *any* Unicode code point (result: `HTTP/(\d)\.(\d)`). 2. The HTTP version was permitting Unicode digits, where only ASCII digits are standards-compliant. 3. Distinct regular expressions for validating HTTP Method and Header field names were used - though both should (at least) apply the common restrictions of rfc9110 `token`. ### PoC `GET / HTTP/1ö1` `GET / HTTP/1.𝟙` `GET/: HTTP/1.1` `Content-Encoding?: chunked` ### Impact Primarily concerns running an aiohttp server without llhttp: 1. **behind a proxy**: Being more lenient than internet standards require could, depending on deployment environment, assist in request smuggling. 2. **directly accessible** or exposed behind proxies relaying malformed input: the unhandled exception could cause excessive resource consumption on the application server and/or its logging facilities. ----- Patch: https://github.com/aio-libs/aiohttp/pull/8074/files
References
- github.com/aio-libs/aiohttp/security/advisories/GHSA-8qpw-xqxj-h4r2 (opens in a new tab)
- github.com/aio-libs/aiohttp/security/advisories/GHSA-gfw2-4jvh-wgfg (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2024-23829 (opens in a new tab)
- github.com/aio-libs/aiohttp/pull/3235 (opens in a new tab)
- github.com/aio-libs/aiohttp/pull/8074 (opens in a new tab)
- github.com/aio-libs/aiohttp/pull/8074/files (opens in a new tab)
- github.com/aio-libs/aiohttp/commit/33ccdfb0a12690af5bb49bda2319ec0907fa7827 (opens in a new tab)
- github.com/aio-libs/aiohttp (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2024-26.yaml (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/02/msg00002.html (opens in a new tab)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ICUOCFGTB25WUT336BZ4UNYLSZOUVKBD (opens in a new tab)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XXWVZIVAYWEBHNRIILZVB3R3SDQNNAA7 (opens in a new tab)