Vulnerability details
CVE-2026-49840
signalwire freeswitch
FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing
CVSS 3.1
9.1Critical
Official description
FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to a software implementation that runs on any commodity hardware. Prior to version 1.11.1, esl_recv_event() parses Content-Length with atol() and passes the result straight to malloc(len + 1) with no sign or magnitude check. A malicious or man-in-the-middle ESL peer can send a frame with a negative Content-Length to corrupt the heap of, or crash, any process linked against libesl, before the client has authenticated to that peer. This issue has been patched in version 1.11.1.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 9.1Critical | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| signalwire | freeswitch | < 1.11.1 | CVEProject cvelistV5 (CNA) |
References and advisories
2- https://github.com/signalwire/freeswitch/security/advisories/GHSA-g597-9fgg-ghg9 x_refsource_CONFIRM
- https://github.com/signalwire/freeswitch/releases/tag/v1.11.1 x_refsource_MISC
Kolun on Telegram @kolunsec
Exploited CVEs, key news and a daily digest
Alerts for this product's next CVEsFollow the product to get new vulnerabilities on Telegram.
Details
- Published
- 2026-06-09
- Last updated
- 2026-06-09
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.31%
Probability of exploitation in 30 days
23.9%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-20Improper Input Validation
- CWE-122Heap-based Buffer Overflow
- CWE-195Signed to Unsigned Conversion Error
- CWE-787Out-of-bounds Write