CVE-2026-45100

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6%, top 55% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Versions 3.4.0-beta through 3.6.5 and 4.0.0-beta contain a buffer overflow in the {s.b64encode} string transformation. The size check for {s.b64encode} only verifies that the input fits within the 64 KB transformation buffer, but base64 encoding expands the data by roughly a third, so an input between about 49,153 and 65,535 bytes produces more output than the buffer can hold and overflows it by up to 21,844 bytes. Because these transformation buffers sit next to each other in memory and are reused for chained transformations, the overflow writes attacker-controlled data into the adjacent buffer and corrupts values used by later transformations processing the same SIP message. A remote attacker can trigger this by sending a SIP message with a large header value (roughly 50,000 bytes or more) when the routing script applies  {s.b64encode}  to attacker-controlled input, making exploitability dependent on the deployment's routing configuration. This issue has been fixed in versions 3.6.6 and 4.0.0-rc1.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
72(Attend)
EG Risk 72/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
45%
KEV
Not listed

Published

August 4, 2026

Last Modified

August 5, 2026

Advisory Details (3)

Auto-updated Aug 29, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available

Buffer Overflow in Base64 Encode Transformation · Advisory · OpenSIPS/opensips · GitHub

https://github.com/OpenSIPS/opensips/security/advisories/GHSA-35fr-6rv9-vp68
github_commit

commit 5f103effaf5f (OpenSIPS/opensips)

Fix landed in OpenSIPS/opensips commit 5f103effaf5f — awaiting tagged release

https://github.com/OpenSIPS/opensips/commit/5f103effaf5f372cccffe0b138f16998eba12668
github_commit

commit 4d23613b6557 (OpenSIPS/opensips)

Fix landed in OpenSIPS/opensips commit 4d23613b6557 — awaiting tagged release

https://github.com/OpenSIPS/opensips/commit/4d23613b65579b073784a07a65d3bf52443a4efb

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:33 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-29 21:42 UTCEG score recompute
  4. 2026-08-28 21:41 UTCEPSS rescore
  5. 2026-08-27 19:57 UTCEG score recompute
  6. 2026-08-27 14:25 UTCEPSS rescore
  7. 2026-08-26 19:09 UTCEG score recompute
  8. 2026-08-26 14:46 UTCEPSS rescore
  9. 2026-08-25 13:54 UTCEG score recompute
  10. 2026-08-25 13:49 UTCEPSS rescore
  11. 2026-08-24 14:48 UTCEG score recompute
  12. 2026-08-24 10:56 UTCEG score recompute
  13. 2026-08-23 04:07 UTCEG score recompute
  14. 2026-08-23 00:19 UTCEPSS rescore
  15. 2026-08-22 01:09 UTCEG score recompute
  16. 2026-08-21 23:49 UTCEPSS rescore
  17. 2026-08-21 02:01 UTCEG score recompute
  18. 2026-08-20 22:55 UTCEPSS rescore
  19. 2026-08-19 18:55 UTCEG score recompute
  20. 2026-08-19 17:04 UTCEPSS rescore
  21. 2026-08-18 18:16 UTCEG score recompute
  22. 2026-08-18 13:48 UTCEPSS rescore
  23. 2026-08-17 17:18 UTCEG score recompute
  24. 2026-08-17 13:47 UTCEPSS rescore
  25. 2026-08-16 17:50 UTCEG score recompute
Show 25 more
  1. 2026-08-16 14:56 UTCEPSS rescore
  2. 2026-08-16 02:25 UTCEG score recompute
  3. 2026-08-16 02:14 UTCEPSS rescore
  4. 2026-08-15 03:20 UTCEG score recompute
  5. 2026-08-15 01:30 UTCEPSS rescore
  6. 2026-08-14 00:23 UTCEG score recompute
  7. 2026-08-13 22:00 UTCEPSS rescore
  8. 2026-08-12 17:26 UTCEG score recompute
  9. 2026-08-12 13:51 UTCEPSS rescore
  10. 2026-08-11 14:26 UTCEG score recompute
  11. 2026-08-11 02:53 UTCEG score recompute
  12. 2026-08-11 00:00 UTCEPSS rescore
  13. 2026-08-09 16:13 UTCEG score recompute
  14. 2026-08-09 13:46 UTCEPSS rescore
  15. 2026-08-08 17:08 UTCEG score recompute
  16. 2026-08-08 16:37 UTCEPSS rescore
  17. 2026-08-07 18:02 UTCEG score recompute
  18. 2026-08-06 14:35 UTCEG score recompute
  19. 2026-08-06 13:46 UTCEPSS rescore
  20. 2026-08-05 19:19 UTCEG score recompute
  21. 2026-08-05 19:17 UTCEPSS rescore
  22. 2026-08-05 15:28 UTCEG score recompute
  23. 2026-08-04 22:31 UTCEG score recompute
  24. 2026-08-04 22:06 UTCEG score recompute
  25. 2026-08-04 22:05 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-45100?
CVE-2026-45100 is a critical vulnerability published on August 4, 2026. OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Versions 3.4.0-beta through 3.6.5 and 4.0.0-beta contain a buffer overflow in the {s.b64encode} string transformation. The size check for {s.b64encode} only verifies that the input fits within the 64 KB transformation buffer,…
When was CVE-2026-45100 disclosed?
CVE-2026-45100 was first published in the National Vulnerability Database on August 4, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-45100 actively exploited?
CVE-2026-45100 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 54.9% of all scored CVEs.
What is the CVSS score of CVE-2026-45100?
CVE-2026-45100 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-45100?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-45100, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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