CVE-2026-26309 json
Envoy has an off-by-one write in JsonEscaper::escapeString()
published 2026-03-10 8 mo ago modified 2026-09-08 2 mo ago also BIT-envoy-2026-26309 , EUVD-2026-10800 , GHSA-56cj-wgg3-x943
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 36%
- public exploits
- 0
- none known
Summary
Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, an off-by-one write in Envoy::JsonEscaper::escapeString() can corrupt std::string null-termination, causing undefined behavior and potentially leading to crashes or out-of-bounds reads when the resulting string is later treated as a C-string. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.
Patch / fix
- bitnami envoy 1.34.13, 1.35.9, 1.36.5, 1.37.1
- envoyproxy envoy 1.34.13, 1.35.9, 1.36.5, 1.37.1
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 8 mo ago
Exploit prediction
0.41% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-56cj-wgg3-x943 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| GitHub | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| NVD | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| OSV | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/envoyproxy/envoy | 1 listed version >=1.36.0, <=1.36.4 >=1.35.0, <=1.35.8 <=1.34.12 |
no fix listed |
| bitnami | envoy | <1.34.13 >=1.35.0, <1.35.9 >=1.36.0, <1.36.5 >=1.37.0, <1.37.1 |
1.34.13 1.35.9 1.36.5 1.37.1 |
Affected products
- envoyproxy envoy
Classification
- Weakness
-
- CWE-193 Off-by-one Error
References
-
github.com
/envoyproxy/envoy/security/advisories/GHSA-56cj-wgg3-x943
web, exploit, vendor-advisory, advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-26309
advisory, web
-
github.com
/envoyproxy/envoy
package
Sources
- CVE List CVE-2026-26309
- GitHub Advisory GHSA-56cj-wgg3-x943
- NVD CVE-2026-26309
- OSV BIT-envoy-2026-26309
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.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.