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Examples / Report #3340109 Saved analysis

Stack Buffer Overflow in cURL Cookie Parsing Leads to RCE

curl · 2025-09-169.4s analysis · $0.012 in model calls

What the report claims

Stack buffer overflow in cURL's cookie parsing mechanism leads to remote code execution.

Compare with curl's recorded outcome

Labeled AI slop

curl's maintainer lists this report as AI slop

Shown for comparison after analysis. The pipeline did not see this label.

ProveIt's finding

Needs a policy review

The code does what the report says, but curl's own policy may exclude it. A maintainer decides.

curl policy: NULL dereferences and crashes
Judgment withdrawn. The answer failed the evidence check.
See the withdrawn model reasoning

The following reasoning failed the citation check and does not support the final finding.

  • The PoC demonstrates a buffer overflow in the reporter's own test code (calling strlen() on an unterminated local buffer), not in cURL's cookie parsing logic.
  • The ASAN stack trace shows the crash at exact_vulnerability_poc.c:124 with no cURL functions involved.
  • No cURL source code was provided, and the deterministic check only confirms CURLOPT_COOKIEFILE exists — not that any cookie parsing code has the claimed flaw.
  • The report's central claim is contradicted by the very evidence it provides: the overflow is in the PoC, not in libcurl.
What still needs checking
  • Actual cURL cookie parsing source code (e.g., lib/cookie.c or similar) showing a stack buffer used without bounds checking
  • A PoC that exercises cURL's HTTP response handling and cookie parser (e.g., via CURLOPT_COOKIEFILE or CURLOPT_COOKIEJAR) and triggers the overflow inside libcurl
How this analysis ran 6 claims · 0 citations verified

Evidence check: the behavior is real; the project's policy section 'NULL dereferences and crashes' may exclude it

Checked against curl master on 2025-09-16 (98d5321530e4). Test evaluation split. Citation verification checks that a referenced line was in the evidence; it does not prove the model interpreted it correctly.

1 · Grounding
grounded
no model · 2 references checked out, 0 did not
2 · Claims
NVIDIA-Nemotron-3-Nano-30B-A3B
6 claims · 4178 tokens · $0.0003
3 · Evidence
0 code snippets
real curl source at 98d5321530e4
4 · Judgment
Nemotron-3-Ultra-550b-a55b
7962 tokens · 6.5s · $0.0120
5 · Receipts
0 of 6 citations verified
every citation must point at code the judge was shown
Inspect the withdrawn draft reply

This draft belongs to the withdrawn judgment. It may contain unsupported claims.

The AddressSanitizer trace you provided shows the stack-buffer-overflow occurring in your PoC's `trigger_exact_overflow()` function (exact_vulnerability_poc.c:124) when it calls `strlen()` on a local 8192-byte buffer that you deliberately left without a null terminator. No cURL functions appear in the stack trace, and the PoC does not invoke any cURL cookie-parsing API. To substantiate a cURL vulnerability, please provide: (1) the specific cURL source file and function where the unbounded `strlen()` or equivalent occurs, and (2) a reproducer that triggers the flaw via libcurl's public API (e.g., an HTTP response with a large Set-Cookie header processed through CURLOPT_COOKIEFILE/COOKIEJAR).

Inspect all claims and source code 6 claims · 0 code excerpts

This model judgment was withdrawn. The claim assessments below are preserved for inspection and may be wrong.

Report claims

C1flaw contradicted

Stack-based buffer overflow occurs when processing maliciously crafted HTTP cookies

Read the reasoning

The PoC creates a local stack buffer `huge_cookie[8192]`, fills it without a null terminator, and calls `strlen()` on it. This is undefined behavior in the reporter's own test code, not a vulnerability in cURL's cookie parsing. The ASAN trace shows the crash at `trigger_exact_overflow exact_vulnerability_poc.c:124`, with no cURL functions in the stack.

exact_vulnerability_poc.c:124
C2location not verifiable

Cookie parsing functionality where string length calculations exceed allocated stack buffer boundaries

Read the reasoning

The referenced file `cookie_vulnerability_hunter.c` is not a cURL source file. The curl_source section states '(no curl code could be retrieved for this report)'. Without actual cURL cookie parsing code, this claim cannot be verified against the project.

cookie_vulnerability_hunter.c:121
C3trigger not verifiable

Oversized cookie data through HTTP responses

Read the reasoning

The reproduction steps in the PoC do not involve HTTP responses or cURL's cookie parser. The claim describes a theoretical attack vector but the provided code does not demonstrate reachability through cURL's HTTP/cookie handling.

exact_vulnerability_poc.c:0
C4impact not verifiable

Remote code execution via stack overflow

Read the reasoning

The impact claim is speculative. The only demonstrated behavior is a stack-buffer-overflow in the PoC's `strlen()` call on an unterminated local buffer. No cURL code path to RCE is shown.

exact_vulnerability_poc.c:0
C5reproduction contradicted

ASAN_OPTIONS="abort_on_error=1" ./exact_poc

Read the reasoning

The reproduction command runs the reporter's standalone test program. It does not exercise cURL's cookie parsing, so it does not reproduce a cURL vulnerability.

exact_vulnerability_poc.c:124
C6impact contradicted

READ of size 8193 at address 0x00016f00a5c0

Read the reasoning

The ASAN trace confirms the overflow occurs in the reporter's PoC code when calling `strlen()` on a non-null-terminated local buffer. No cURL symbols appear in the stack trace.

exact_vulnerability_poc.c:124
Read the original report (excerpt)

Full report on HackerOne ↗

## Summary I discovered a critical stack-based buffer overflow vulnerability in cURL's cookie parsing mechanism that can lead to remote code execution. The vulnerability occurs when processing maliciously crafted HTTP cookies, affecting all applications that use libcurl for HTTP requests. ## Description During security research on cURL's cookie handling implementation, I identified a stack buffer overflow in the cookie parsing logic. The vulnerability allows remote attackers to trigger memory corruption by sending oversized cookie data through HTTP responses. ### Technical Details #### Vulnerability Location The vulnerability occurs in the cookie parsing functionality where string length calculations exceed allocated stack buffer boundaries. #### Root Cause Analysis 1. **Buffer Size Mismatch:** Cookie processing code reads beyond allocated stack buffer 2. **Unsafe String Operations:** `strlen()` operation on cookie data exceeds buffer boundaries 3. **Stack Memory Corruption:** Read of 8,193 bytes in a buffer allocated for 8,192 bytes 4. **Multi-threaded Context:** Issue manifests in threaded environments #### AddressSanitizer Detection ``` ==5415==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x00016f00a5c0 READ of size 8193 at 0x00016f00a5c0 thread T1 #0 0x000101676c34 in strlen+0x1b0 #1 0x000100f94c38 in cookie_overflow_hunter cookie_vulnerability_hunter.c:121 Address 0x00016f00a5c0 is located in stack of thread T1 at offset 8224 in frame This frame has 4 object(s): [32, 8224) 'huge_cookie' (line 109) <- 8KB buffer [8480, 9504) 'huge_name_cookie' (line 128) <- Adjacent buffer [9632, 10144) 'huge_name' (line 129) <- Adjacent buffer [10208, 10464) 'multi_cookie' (line 137) <- Adjacent buffer ``` ## Steps to Reproduce ### Environment Setup ```bash # Set AddressSanitizer options for detailed detection export ASAN_OPTIONS="abort_on_error=1:halt_on_error=1" # Compile the verified PoC with memory safety flags gcc -fsanitize=address -g -o exact_poc exact_vulnerability_poc.c -lcurl ``` ### Verified Reproduction Steps 1. **Save the PoC code** to `exact_vulnerability_poc.c` (code provided above) 2. **Compile with AddressSanitizer:** ```bash gcc -fsanitize=address -g -o exact_poc exact_vulnerability_poc.c -lcurl ``` 3. **Execute the PoC:** ```bash ASAN_OPTIONS="abort_on_error=1" ./ex …

Source code

No source code was retrieved for this analysis. The evidence may be incomplete.