Redis — CWE-407 Disclosure Brief

2026-03-27 · Patch available — awaiting upstream merge

Finding

Three O(n²) defects in Redis's set intersection, ACL channel management, and ACL key-pattern management. All use linear list scans (lpFind, listSearchKey) in paths that are called per-command or per-ACL-rule. Patches ready for upstream review.

The Defects

redis-0001 (PATCHED — HIGH): t_set.c

/* Inside SINTER listpack inner loop — per element: */
/* lpFind() — O(M) listpack scan per element of set intersection */
if (lpFind(lp, element, ...) != NULL) { ... }
/* O(N×M) per SINTER command */

lpFind performs O(M) linear scan per element during SINTER listpack intersection. For N elements in one set and M in the other: O(N × M) per SINTER. Measured ratio: 128×.

redis-0002 (PATCHED — HIGH): acl.c

/* getUpcomingChannelList() — listSearchKey O(n) per pattern: */
/* O((S×C)²) when checking channel superset */
listSearchKey(selector->channels, channel)  /* O(n) linear scan */

listSearchKey O(n) scan per pattern in channel list management. O((S×C)²) total. Measured ratio: 250×.

redis-0003 (PATCHED — HIGH): src/acl.c:1103,1122

/* ACLSetSelector — listSearchKey(selector->patterns, newpat) O(P) per rule: */
/* O(P²) when adding P key-patterns via ACL SETUSER */
if (listSearchKey(selector->patterns, newpat) != NULL) { ... }

listSearchKey O(P) dedup scan per key-pattern rule in ACLSetSelector. For P patterns: O(P²) total. Measured ratio: 500×.

Complexity Proof

redis-0001: For N=128 elements, M=128 elements per SINTER:

O(N×M) = 16,384 comparisons
Fixed: hash set → O(N + M)
128× measured ratio.

redis-0002: 250× measured ratio on ACL channel superset checks.

redis-0003: For P=500 key-patterns:

O(P²) = 250,000 comparisons
Fixed: parallel dict → O(P)
500× measured ratio.

Impact

redis-0001 affects all Redis deployments using SINTER on listpack-encoded sets (sets with few small elements — common in practice). redis-0002/0003 affect all Redis 7.0+ deployments using ACL selectors with channels and key patterns — the primary access control mechanism. Redis is used in virtually every web-scale application stack.

The Fix

redis-0001: Replace lpFind inner loop with a hash set built from the smaller set.

redis-0002: Replace listSearchKey with HashSet for channel tracking.

redis-0003: Add a parallel dict alongside selector->patterns for O(1) dedup:

/* Before */
if (listSearchKey(selector->patterns, newpat) != NULL) { ... }

/* After */
/* CWE-407 fix: parallel dict for O(1) pattern dedup instead of O(P) listSearchKey. */
if (dictFind(selector->patterns_dict, newpat) != NULL) { ... }

Patch

defects/redis/patch/redis-0001-0002-0003-sinter-acl-hashset.patch

What We Ask

Confirm receipt and assign a GitHub Security Advisory or issue reference.
Validate the patch against your SINTER and ACL test suites.
Assess CVE eligibility — redis-0003 measured at 500× on ACL key-pattern management.
Coordinate a disclosure date — we are targeting 90 days from first contact.

Contact: see cover email. This brief is confidential until coordinated disclosure.

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