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FA-27901 / HTTP redirects / Open access

Validate raw target text before any URL normalization: nul detection · case 01

An interior NUL evades validation.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The nul-detection decision uses "raw.endswith('\\x00')"; this violates the stipulated controller policy.

VERIFIED REPAIR

At this decision use "'\\x00' in raw", preserving the other controller outputs.

Unsuccessful approach: The partial repair uses "raw.startswith('\\x00')" and still fails an explicit boundary or control.

Case contract

Validate raw target text before any URL normalization. The explicit fixture inputs and outputs define a bounded offline policy; request identity must accompany the decision.

Why this case matters

Models a redirect controller decision before following a target or exposing a redirect result.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, raw):
    return {'request': request, 'decision': ['\r' in raw or '\n' in raw, '\t' in raw.strip(' \t'), raw.endswith('\x00'), bool(re.search(r'%(?![0-9A-Fa-f]{2})', raw)), '\\' in raw]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', '/a\rb\tc\x00d%G0\\e'), {'request': '/requests/' + str(N) + '/0', 'decision': [True, True, True, True, True]})
check('fixture 2', solve('/requests/' + str(N) + '/1', '\t/a%20b\t'), {'request': '/requests/' + str(N) + '/1', 'decision': [False, False, False, False, False]})
check('fixture 3', solve('/requests/' + str(N) + '/2', '/a\nb'), {'request': '/requests/' + str(N) + '/2', 'decision': [True, False, False, False, False]})
check('fixture 4', solve('/requests/' + str(N) + '/3', '/a%'), {'request': '/requests/' + str(N) + '/3', 'decision': [False, False, False, True, False]})
check('fixture 5', solve('/requests/' + str(N) + '/4', '/normal'), {'request': '/requests/' + str(N) + '/4', 'decision': [False, False, False, False, False]})
check('fixture 6', solve('/requests/' + str(N) + '/5', ''), {'request': '/requests/' + str(N) + '/5', 'decision': [False, False, False, False, False]})
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 1{'decision': [True, True, False, True, True], 'request': '/requests/1/0'}{'decision': [True, True, True, True, True], 'request': '/requests/1/0'}Failed
fixture 2{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}Passed

SHA-256 / 8778668ba05c66fd848b46f98a0b4bdb726756bef39372c0f728a5a33ff51431

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, raw):
    return {'request': request, 'decision': ['\r' in raw or '\n' in raw, '\t' in raw.strip(' \t'), raw.startswith('\x00'), bool(re.search(r'%(?![0-9A-Fa-f]{2})', raw)), '\\' in raw]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', '/a\rb\tc\x00d%G0\\e'), {'request': '/requests/' + str(N) + '/0', 'decision': [True, True, True, True, True]})
check('fixture 2', solve('/requests/' + str(N) + '/1', '\t/a%20b\t'), {'request': '/requests/' + str(N) + '/1', 'decision': [False, False, False, False, False]})
check('fixture 3', solve('/requests/' + str(N) + '/2', '/a\nb'), {'request': '/requests/' + str(N) + '/2', 'decision': [True, False, False, False, False]})
check('fixture 4', solve('/requests/' + str(N) + '/3', '/a%'), {'request': '/requests/' + str(N) + '/3', 'decision': [False, False, False, True, False]})
check('fixture 5', solve('/requests/' + str(N) + '/4', '/normal'), {'request': '/requests/' + str(N) + '/4', 'decision': [False, False, False, False, False]})
check('fixture 6', solve('/requests/' + str(N) + '/5', ''), {'request': '/requests/' + str(N) + '/5', 'decision': [False, False, False, False, False]})
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 1{'decision': [True, True, False, True, True], 'request': '/requests/1/0'}{'decision': [True, True, True, True, True], 'request': '/requests/1/0'}Failed
fixture 2{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}Passed

SHA-256 / 6578d9b8d1fa06a1bf887ca08b00e1adde9f466a7d86234a01d6f0adec5928a0

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json
from urllib.parse import urlsplit, unquote, quote
import posixpath
import re
N = 1
observations = []
def solve(request, raw):
    return {'request': request, 'decision': ['\r' in raw or '\n' in raw, '\t' in raw.strip(' \t'), '\x00' in raw, bool(re.search(r'%(?![0-9A-Fa-f]{2})', raw)), '\\' in raw]} 
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('/requests/' + str(N) + '/0', '/a\rb\tc\x00d%G0\\e'), {'request': '/requests/' + str(N) + '/0', 'decision': [True, True, True, True, True]})
check('fixture 2', solve('/requests/' + str(N) + '/1', '\t/a%20b\t'), {'request': '/requests/' + str(N) + '/1', 'decision': [False, False, False, False, False]})
check('fixture 3', solve('/requests/' + str(N) + '/2', '/a\nb'), {'request': '/requests/' + str(N) + '/2', 'decision': [True, False, False, False, False]})
check('fixture 4', solve('/requests/' + str(N) + '/3', '/a%'), {'request': '/requests/' + str(N) + '/3', 'decision': [False, False, False, True, False]})
check('fixture 5', solve('/requests/' + str(N) + '/4', '/normal'), {'request': '/requests/' + str(N) + '/4', 'decision': [False, False, False, False, False]})
check('fixture 6', solve('/requests/' + str(N) + '/5', ''), {'request': '/requests/' + str(N) + '/5', 'decision': [False, False, False, False, False]})
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 1{'decision': [True, True, True, True, True], 'request': '/requests/1/0'}{'decision': [True, True, True, True, True], 'request': '/requests/1/0'}Passed
fixture 2{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}{'decision': [False, False, False, False, False], 'request': '/requests/1/1'}Passed
fixture 3{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}{'decision': [True, False, False, False, False], 'request': '/requests/1/2'}Passed
fixture 4{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}{'decision': [False, False, False, True, False], 'request': '/requests/1/3'}Passed
fixture 5{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}{'decision': [False, False, False, False, False], 'request': '/requests/1/4'}Passed
fixture 6{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}{'decision': [False, False, False, False, False], 'request': '/requests/1/5'}Passed

SHA-256 / 3788a590222f810d8e0c6e9edf5c7d7f80c1461c85ea2694df3c56077ede76eb

Verification & scope

Stipulated offline redirect policy, not a complete HTTP, browser, URL, cache, or security implementation. Numbered variants vary request correlation identity. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:41:29.226834+00:00.

Case digest / 8932c5e1dbd4e5ae75bbb381c4d74c37d7912a52deb5c6c85c2c8c82a4db3204