CVE-2026-50813: SQLite Information Disclosure Vulnerability

CVE-2026-50813 Overview

CVE-2026-50813 is a buffer overread vulnerability in SQLite's Session Extension. The flaw exists in the changeset concat and changegroup merge path before the Fossil check-in 869a51ae84df. A local attacker who convinces a user to process a crafted changeset can read out-of-bounds memory and trigger process termination. The issue is tracked as CWE-126: Buffer Over-read.

Critical Impact
Local attackers can leak sensitive process memory and crash applications that consume attacker-supplied SQLite changesets through the Session Extension.

Affected Products

SQLite versions prior to Fossil check-in 869a51ae84df
Applications embedding the SQLite Session Extension (ext/session/sqlite3session.c)
Downstream software distributing vulnerable SQLite builds

Discovery Timeline

2026-07-08 - CVE-2026-50813 published to NVD
2026-07-08 - Last updated in NVD database

Technical Details for CVE-2026-50813

Vulnerability Analysis

The defect resides in the SQLite Session Extension changeset processing logic. When merging changesets through sqlite3changeset_concat() or the changegroup API, the parser reads variable-length integer fields that encode record sizes. A corrupt changeset can supply a signed varint whose top bit is set, causing the returned length to be interpreted as a negative value. Downstream code uses this length as an unsigned offset, leading to a read past the end of the input buffer.

An attacker delivers a malicious changeset file to a user or application that trusts SQLite changeset input. Processing the file leaks adjacent heap memory into subsequent output or crashes the host process, producing a denial-of-service condition. The vulnerability requires local delivery of the crafted artifact and user interaction to trigger parsing.

Root Cause

The sessionVarintGet() helper called getVarint32() and returned the raw 32-bit value without masking the sign bit. Negative or oversized decoded values propagated into buffer arithmetic used by the changeset iterator, allowing reads outside the allocated changeset blob.

Attack Vector

Exploitation requires local file delivery and user interaction, such as opening or importing a crafted changeset. No privileges are required on the target system, but the attacker cannot trigger the flaw remotely without additional user action.

 ** bytes read.
 */
 static int sessionVarintGet(const u8 *aBuf, int *piVal){
-  return getVarint32(aBuf, *piVal);
+  int ret = getVarint32(aBuf, *piVal);
+  *piVal = (*piVal & 0x7FFFFFFF);
+  return ret;
 }

Source: SQLite commit c597ed79d1bd03f57198d10d1f431adda293cf2e. The patch masks the decoded varint with 0x7FFFFFFF, clearing the sign bit and preventing negative length propagation.

Detection Methods for CVE-2026-50813

Indicators of Compromise

Unexpected crashes or segmentation faults in processes invoking sqlite3changeset_concat() or sqlite3changegroup_add()
Presence of untrusted .changeset or session blob files delivered through email, shared storage, or removable media
Application logs referencing SQLITE_CORRUPT or SQLITE_RANGE errors during changeset merges

Detection Strategies

Inventory binaries statically or dynamically linking SQLite and compare embedded versions against the fixed Fossil check-in 869a51ae84df
Monitor endpoints for processes that read attacker-controlled changeset files followed by abnormal memory-read patterns
Enable AddressSanitizer or Valgrind in development pipelines to surface overreads while fuzzing changeset inputs

Monitoring Recommendations

Alert on repeated crashes of applications known to invoke the SQLite Session Extension
Track file writes creating changeset artifacts in user download or temp directories, then correlate with subsequent SQLite process activity
Ingest host telemetry into a centralized data lake to correlate crash events with the origin of the changeset file

How to Mitigate CVE-2026-50813

Immediate Actions Required

Upgrade SQLite to a build that includes Fossil check-in 869a51ae84df or later
Rebuild and redistribute any downstream applications that statically link the vulnerable Session Extension
Restrict acceptance of changeset files to trusted, authenticated sources

Patch Information

The upstream fix is committed as SQLite commit c597ed79d1bd03f57198d10d1f431adda293cf2e and referenced by SQLite Fossil check-in 869a51ae84df. The change in ext/session/sqlite3session.c masks the decoded varint value with 0x7FFFFFFF so oversized or negative lengths cannot flow into buffer offset arithmetic. Additional analysis is available in the researcher gist.

Workarounds

Disable or avoid the Session Extension in builds that do not require changeset merging
Validate changeset provenance with cryptographic signatures before invoking sqlite3changeset_concat() or changegroup APIs
Sandbox processes that consume third-party changeset files to contain memory disclosure impact

bash

# Verify the SQLite source tree includes the fix
cd sqlite
fossil update 869a51ae84df
./configure && make
./sqlite3 --version