CVE-2026-11702: Bytes::Random::Secure::Tiny PRNG State Sharing in Forked Processes

Technical summary

CVE-2026-11702 is a cryptographic weakness in Bytes::Random::Secure::Tiny (Perl) caused by shared PRNG state across forked processes. When an object is instantiated before a fork() call, the internal state of the pseudo-random number generator is inherited unchanged by child processes. Without re-seeding, each process produces identical random streams deterministically. This violates the core assumption of secure random generation: that secrets generated in different execution contexts are independent. The vulnerability is classified under CWE-335 (Incorrect Restriction of Rendered UI Layers or Frames), though it more directly reflects insufficient state isolation in cryptographic operations.

Business impact

For organizations deploying multi-process Perl applications that rely on Bytes::Random::Secure::Tiny for secrets—session tokens, API keys, nonces, or encryption material—this vulnerability allows attackers to predict generated values with high confidence. In web applications using preforked servers or worker pools, an attacker observing one process's output can derive secrets from all sibling processes. This undermines authentication, breaks session isolation, and may expose encryption keys. The impact extends to any application where secret predictability directly compromises confidentiality or integrity.

Affected systems

Perl applications using Bytes::Random::Secure::Tiny library through version 1.011 are affected when deployed in multi-process architectures. Common scenarios include preforked web servers (e.g., Catalyst, Dancer, or raw fork-based workers), parallel batch processors, and microservice containers that fork for concurrency. Single-process applications and those that initialize the PRNG after forking are not vulnerable.

Exploitability

Exploitability is practical if an attacker can observe random output from one process and predict output from others—plausible in scenarios where secrets are exposed via timing channels, side channels, or direct observation of session tokens. No code injection or authentication bypass is required; exploitation relies on the mathematical property that identical PRNG state produces identical output. The CVSS score of 7.5 (HIGH) reflects high confidentiality impact with network-accessible attack vector and no privilege requirements, though actual risk depends on how secrets are exposed and whether they are reused across processes.

Remediation

Upgrade Bytes::Random::Secure::Tiny to a patched version that re-seeds the PRNG after process fork, ensuring each child inherits a unique state. Verify the fixed version against the vendor's advisory. As a temporary mitigation, initialize a new Bytes::Random::Secure::Tiny object in each child process after fork() rather than inheriting a pre-fork object. For applications unable to patch immediately, consider using OS-level randomness sources (e.g., /dev/urandom) via alternative Perl modules that guarantee per-process independence.

Patch guidance

Check the Bytes::Random::Secure::Tiny distribution on CPAN for versions released after June 2026. Patched versions will include logic to detect fork events (via $$ PID tracking or POSIX::_exit hooks) and re-seed automatically. Installations should verify against the module's official advisory before deploying. Test multi-process deployments after patching to confirm randomness independence across processes.

Detection guidance

Audit Perl dependency manifests and installed module versions to identify Bytes::Random::Secure::Tiny ≤1.011 in production. Review code for patterns where a Bytes::Random::Secure::Tiny object is created before fork() calls; flag these as high priority. Monitor runtime for fork() calls in applications that generate secrets, and correlate process creation timestamps with secret generation logs to detect potential patterns. No network-visible signature exists; detection requires code review and inventory management.

Why prioritize this

This is a HIGH-severity cryptographic weakness affecting core security operations in multi-process Perl applications. While not yet in CISA's Known Exploited Vulnerabilities catalog, the vulnerability requires only a code update and poses direct confidentiality risk to applications handling authentication tokens, session IDs, or encryption keys. Organizations should prioritize patching for any Perl applications that fork and generate secrets, particularly those exposed to untrusted networks.

Risk score, explained

CVSS 7.5 reflects a network-accessible vulnerability with high confidentiality impact (complete disclosure of secrets), no authentication required, and no user interaction. The score assumes secrets are either exposed to attackers or can be validated through timing or cryptographic attacks. Actual organizational risk depends on whether Perl applications are internet-facing, whether secrets are reused across processes, and whether alternative defenses (e.g., HSM-based key generation) are in place.

Frequently asked questions