Starch versions 0.14 and earlier generate session ids insecurely

published 2025-09-20 13 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-30364

cvss: 9.1; 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 29%
public exploits: 0; none known

Starch versions 0.14 and earlier generate session ids insecurely.

The default session id generator returns a SHA-1 hash seeded with a counter, the epoch time, the built-in rand function, the PID, and internal Perl reference addresses. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage.

Predicable session ids could allow an attacker to gain access to systems.

Patch / fix

links 2

github.com/bluefeet/Starch@5573449 commit
github.com/bluefeet/Starch#5 pull request

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 13 mo ago (2025-09-22)

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

BLUEFEET Starch

Classification

Weakness

CWE-340 Generation of Predictable Numbers or Identifiers
CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

References

Sources

CVE List CVE-2025-40925
NVD CVE-2025-40925

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.

Summary