CVE-2026-53503 json
Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
published 2026-07-31 3 mo ago modified 2026-09-08 2 mo ago also GHSA-cqjp-jf4r-h5q9 , PYSEC-2026-3619 , EUVD-2026-51609
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.8%
- EPSS 0.8% chance of exploitation in 30 days, percentile 55%
- public exploits
- 0
- none known
Summary
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(<matrix>, <columns>, <should_normalize>) filter passes the user-controlled <columns> value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns > 0. When columns=0, the C code triggers undefined behavior; on x86_64 this reliably results in a fatal divide-by-zero trap (SIGFPE) and crashes the Thumbor process, causing a remote denial of service. This issue is fixed in 7.8.0.
Patch / fix
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 3 mo ago
Exploit prediction
0.75% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| OSV | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | thumbor | <7.8.0 |
7.8.0 |
Affected products
- thumbor thumbor
Classification
References
-
github.com
/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73
web
-
github.com
/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9
exploit, web
-
github.com
/thumbor/thumbor/releases/tag/7.8.0
web
-
github.com
/thumbor/thumbor
package
-
pypi.org
/project/thumbor
package
-
github.com
/advisories/GHSA-cqjp-jf4r-h5q9
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-53503
advisory
Sources
- CVE List CVE-2026-53503
- GitHub Advisory GHSA-cqjp-jf4r-h5q9
- NVD CVE-2026-53503
- OSV PYSEC-2026-3619
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.